text: // Exercise 13.12 Solution: CommissionEmployee.h
  // CommissionEmployee class derived from Employee.
  #ifndef COMMISSION_H
  #define COMMISSION_H
  
  #include "Employee.h" // Employee class definition
  
  class CommissionEmployee : public Employee 
  {
  public:
     CommissionEmployee( const string &, const string &,
        const string &, int, int, int, double = 0.0, double = 0.0 );
  
     void setCommissionRate( double ); // set commission rate
     double getCommissionRate() const; // return commission rate
  
     void setGrossSales( double ); // set gross sales amount
     double getGrossSales() const; // return gross sales amount
  
     // keyword virtual signals intent to override
     virtual double earnings() const; // calculate earnings
     virtual void print() const; // print CommissionEmployee object
  private:
     double grossSales; // gross weekly sales
     double commissionRate; // commission percentage
  }; // end class CommissionEmployee
  
  #endif // COMMISSION_H
  
  /**************************************************************************
   * (C) Copyright 1992-2008 by Deitel & Associates, Inc. and               *
   * Pearson Education, Inc. All Rights Reserved.                           *
   *                                                                        *
   * DISCLAIMER: The authors and publisher of this book have used their     *
   * best efforts in preparing the book. These efforts include the          *
   * development, research, and testing of the theories and programs        *
   * to determine their effectiveness. The authors and publisher make       *
   * no warranty of any kind, expressed or implied, with regard to these    *
   * programs or to the documentation contained in these books. The authors *
   * and publisher shall not be liable in any event for incidental or       *
   * consequential damages in connection with, or arising out of, the       *
   * furnishing, performance, or use of these programs.                     *
   **************************************************************************/
  